1. Field of the Invention
The present invention relates to a technology of an optical connecting method that is suitable to connect a single core and multicore optical fiber. The present invention also relates to an optical connection structure and a manufacturing method for the same, and in particular, relates to a technology suitable to connect a single core and multicore optical fiber.
Priority is claimed on Japanese Patent Application No. 2004-169380, filed on Jun. 8, 2004, Japanese Patent Application No. 2004-115421, filed on Apr. 9, 2004, Japanese Patent Application No. 2004-154770, filed on May 25, 2004, and Japanese Patent Application No. 2004-157703, filed on May 27, 2004, the contents of which is incorporated herein by reference.
2. Description of Related Art
The present invention relates to a technology of an optical connecting method that is suitable to connect a single core and multicore optical fiber.
In the case of connecting optical fibers to each other by an optical connecting part, which is used for optical communications widely, and in the case of connecting optical components to each other by an optical fiber on an optical module substrate, there is a method to obtain contact force between end faces of optical fibers or between an end face of an optical fiber and the end face of an optical component from a stress that has occurred by a flexure of the optical fiber. A method shown in FIGS. 7A to 7C is known for this kind of an optical connecting method (for example, refer to Japanese Published Unexamined Patent Application, First Publication No. 08-15567). Namely, in FIGS. 7A to 7C, while a first optical fiber 101 is installed in a first plug 103 in the state which is slidable in the axial direction of the optical fiber, a second optical fiber 102 is secured by a securing component 105 to a second plug 104 (FIG. 7A). At the position where the first and the second optical fibers are aligned, the first plug 103 and the second plug 104 are secured to face each other (FIG. 7B). When a stress to move the first optical fiber in the right direction of the figure is applied thereafter, the first optical fiber 101 abuts against the second optical fiber 102, and bends (FIG. 7C). When the first optical fiber 101 is secured to the first plug 103 with the securing component 105 in this state, the state where the stress by the flexure is applied to the end face of the optical fibers is maintained, and the optical connection is completed. In the present method, however, the stress needs to be applied in order to move the first optical fiber in the right direction, but, it is not easy to give a predetermined stress and a fixed movement, and an excessive stress and movement cause a problem to damage the optical fiber. In addition, there is a need to ensure a space in the rear of the plug for the stress and the movement in the axial direction of the optical fiber. Thus the flexibility of placement of optical components connected to the optical fibers is limited, causing a problem not to be able to use the space on the optical module substrate effectively.
On the other hand, a method of FIGS. 8A and 8B is also known (for example, refer to Japanese Published Unexamined Patent Application, First Publication No. 2000-235132). In the method of FIGS. 8A and 8B, the first optical fiber 101 is secured to the first plug 103, and the second optical fiber 102 to the second plug 104 by the securing component 105. The first optical fiber 101 slightly sticks out from the end of the plug 103, and the tip of the second optical fiber in a position of the end of the plug 104 (FIG. 8A). In this state a stress is applied so that the end of the first plug 103 is brought into close contact with the end of the second plug 104 at the position where the first and the second optical fibers are aligned. Thus the optical fiber bends, and a relative position of the plug 103 and the plug 104 is secured side in this state (FIG. 8B). This method enables control over the quantity of the flexure, namely, control over the stress of the flexure by the length of the optical fiber which initially sticks out from the end of the plug, however, because the optical fibers are aligned in the state where the tip of the first optical fiber sticks out from the plug, the tip of the optical fibers is easily damaged.
As described above, in the optical connecting method to obtain the contact force between the end faces of the optical fibers from the stress that has occurred by the flexure of the optical fiber, there has been no easy connecting method to control the flexural quantity, namely, the quantity of force to the end face of the optical fiber by the flexure easily, and not to cause damage to the tip of the optical fiber when aligning the optical fibers, and without a need for space in the rear of the plug to move the optical fiber after aligning the optical fibers.
There are connectors for which types are FC, SC, MU, and LC for an optical fiber of single core connection and types such as MPO, MPX, and MTP for multicore connection. These connectors generally enable connection by abutting the fibers from the axial direction of the optical fiber. For example, in an optical connecting part of MPO type, the plugs are positioned inside an internal housing integrated in an adapter by inserting the plugs in the adapter from both sides, and MT connector ferrules held on the tips of the plugs abut against each other to be connected.
In particular, although the push-pull method that the insertion and extraction in the axial direction of the optical fibers are easily performed has been suggested, because in the push-pull connector the optical fibers are inserted and extracted in the axial direction of the connected optical fibers, it is easy to connect the optical fibers when connecting to the adapter which is installed in a device wall such as a backplane.
Moreover, in a conventional optical connection structure, when a connector is used for optical fiber connection on a printed board (for example, a motherboard) or in a device, the optical fibers are in many cases connected to each other by mounting the optical connecting part on the tip of the optical fiber connected to various optical components and optical modules. In that case, the optical fiber may be inserted and extracted while the optical fiber connected to an optical component or an optical module bends in order to carry out the insertion and extraction.
On the other hand, as a technology related to this kind, it has been proposed that a connection means for connecting a pair of the abut tips of the optical fibers by abutting them against each other comprises a base formed in a center of the top surface and a cover attached to the top surface side of this base (for example, refer to Japanese Published Unexamined Patent Application, First Publication No. 08-240731 (pages 2 to 4, FIG. 1 to FIG. 3)).
However, in the conventional optical connection structure, when inserting and extracting the optical fiber while the optical fiber connected to an optical component and an optical module bends, there is a concern that an excessive force by flexure acts on a fixed point of the optical module of the optical fiber so that the securing part is damaged.
In addition, in the conventional optical connection structure body, a field of vision of a worker to the insertion and extraction direction becomes inferior. Therefore, working hours are lengthened, and when inserting, there is a concern that the optical fiber breaks a ferrule end and touches a sleeve and a shaft for a guide to cause fracture or damage. Furthermore, other devices cannot be placed freely or cannot even be installed because there is a need to ensure a space for inserting and extracting the connector, thus the space on the substrate cannot be used effectively.
Furthermore, in the conventional optical connection structure body, the detachment direction is not stable, and the connector of the optical fiber comes in contact with peripheral components in reaction so that there is a concern that the optical fiber or the peripheral components are damaged. Also, when a latch mechanism is used to shorten connection times and to improve a connection workability because the latch mechanism simplifies the detachable movement, the latch engages at the time of the insertion and removal to maintain the pressing strength applied on the ferrule with stability. However, the structure becomes complicated and the number of components increases with this method, so that great time and expense are necessary for a design of the optical connecting part, causing an increase in costs.
On the other hand, there has been no consideration in Japanese Published Unexamined Patent Application, First Publication No. 08-240731 appropriately extending the optical fiber to be connected after bending.
Conventionally in an optical circuit structure comprising a plurality of optical function components, a light transmitting medium, and an optical connecting part, the optical function components are connected mutually by connecting the optical circuit on a substrate or in a package of another optical circuit or a light transmitting medium. As this kind of method to connect the light transmitting medium to another light transmitting medium, there are fusion splicing, a mechanical splicer, and an optical connecting part (for example, refer to Japanese Published Unexamined Patent Application, First Publication No. 08-240731 (pages 2 to 4, FIGS. 47 to 49)).
Moreover, among various connecting methods described above, the fusion splicing and the mechanical splicer need to attach a light transmitting medium such as an optical fiber to a connection device in assembling and maintenance checks of the optical circuit. On this account an extra length becomes necessary for the light transmitting medium, and thereby extra length of the light transmitting medium, the light transmitting medium is bulky on the motherboard or in the device, and an excessive space is necessary, causing a problem that the size of the optical circuit increases.
In addition, the optical connecting part is mounted on the light transmitting medium of the optical circuit, so that when the light transmitting medium is drawn from the optical connecting part and the optical circuit, a great stress is applied to the light transmitting medium because the position relationship between the optical connecting part and the light transmitting medium is not fixed, thus there is a concern for damage.
Furthermore, because the fusion splicing and the mechanical splice are mainly used as a permanent connection, when the optical circuit is checked on the printed board (for example, a motherboard) or in the device, mating and demating are impossible, thus it is difficult to perform a maintenance check of the optical function components individually. On this account when there is a malfunction in the optical circuit, it is necessary to change the printed board or even the whole device, causing a problem economically.
Furthermore, a large reinforcement sleeve is necessary for joint protection in the fusion splicing, and the splicer size is large in the mechanical splice. Furthermore, an optical connecting part of a current push-pull type is large in size. Thus, a large installation space is necessary by these connecting methods to ensure space for the insertion and extraction, causing a need to consider placement of another module.
There is a method that the optical connecting part of the push-pull type is mounted on the substrate end and that the substrate is inserted and extracted in parallel to the substrate surface, although, when a small module substrate is mounted on a large-sized printed board such as a motherboard, the substrate needs to be horizontally moved when connecting optically, and a wider range of work space for connection is necessary. Thus, there is a problem that the space cannot be used effectively due to the mentioned causes. Furthermore, when the substrate is hard and cannot be transformed, it becomes difficult to attach the optical connecting part to opposite sides of the substrate for connection, causing limitation in the design of the optical circuit.